diff options
Diffstat (limited to 'arch/powerpc/kernel/watchdog.c')
| -rw-r--r-- | arch/powerpc/kernel/watchdog.c | 93 |
1 files changed, 74 insertions, 19 deletions
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 588f54350d19..af16a835ddec 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -85,10 +85,36 @@ static DEFINE_PER_CPU(u64, wd_timer_tb); /* SMP checker bits */ static unsigned long __wd_smp_lock; +static unsigned long __wd_reporting; static cpumask_t wd_smp_cpus_pending; static cpumask_t wd_smp_cpus_stuck; static u64 wd_smp_last_reset_tb; +/* + * Try to take the exclusive watchdog action / NMI IPI / printing lock. + * wd_smp_lock must be held. If this fails, we should return and wait + * for the watchdog to kick in again (or another CPU to trigger it). + * + * Importantly, if hardlockup_panic is set, wd_try_report failure should + * not delay the panic, because whichever other CPU is reporting will + * call panic. + */ +static bool wd_try_report(void) +{ + if (__wd_reporting) + return false; + __wd_reporting = 1; + return true; +} + +/* End printing after successful wd_try_report. wd_smp_lock not required. */ +static void wd_end_reporting(void) +{ + smp_mb(); /* End printing "critical section" */ + WARN_ON_ONCE(__wd_reporting == 0); + WRITE_ONCE(__wd_reporting, 0); +} + static inline void wd_smp_lock(unsigned long *flags) { /* @@ -151,6 +177,7 @@ static bool set_cpu_stuck(int cpu, u64 tb) static void watchdog_smp_panic(int cpu, u64 tb) { + static cpumask_t wd_smp_cpus_ipi; // protected by reporting unsigned long flags; int c; @@ -160,11 +187,26 @@ static void watchdog_smp_panic(int cpu, u64 tb) goto out; if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) goto out; - if (cpumask_weight(&wd_smp_cpus_pending) == 0) + if (!wd_try_report()) goto out; + for_each_online_cpu(c) { + if (!cpumask_test_cpu(c, &wd_smp_cpus_pending)) + continue; + if (c == cpu) + continue; // should not happen + + __cpumask_set_cpu(c, &wd_smp_cpus_ipi); + if (set_cpu_stuck(c, tb)) + break; + } + if (cpumask_empty(&wd_smp_cpus_ipi)) { + wd_end_reporting(); + goto out; + } + wd_smp_unlock(&flags); pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n", - cpu, cpumask_pr_args(&wd_smp_cpus_pending)); + cpu, cpumask_pr_args(&wd_smp_cpus_ipi)); pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n", cpu, tb, wd_smp_last_reset_tb, tb_to_ns(tb - wd_smp_last_reset_tb) / 1000000); @@ -174,22 +216,14 @@ static void watchdog_smp_panic(int cpu, u64 tb) * Try to trigger the stuck CPUs, unless we are going to * get a backtrace on all of them anyway. */ - for_each_cpu(c, &wd_smp_cpus_pending) { - bool empty; - if (c == cpu) - continue; - /* Take the stuck CPUs out of the watch group */ - empty = set_cpu_stuck(c, tb); + for_each_cpu(c, &wd_smp_cpus_ipi) { smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000); - if (empty) - break; + __cpumask_clear_cpu(c, &wd_smp_cpus_ipi); } - } - - wd_smp_unlock(&flags); - - if (sysctl_hardlockup_all_cpu_backtrace) + } else { trigger_allbutself_cpu_backtrace(); + cpumask_clear(&wd_smp_cpus_ipi); + } /* * Force flush any remote buffers that might be stuck in IRQ context @@ -200,6 +234,8 @@ static void watchdog_smp_panic(int cpu, u64 tb) if (hardlockup_panic) nmi_panic(NULL, "Hard LOCKUP"); + wd_end_reporting(); + return; out: @@ -213,8 +249,6 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb) struct pt_regs *regs = get_irq_regs(); unsigned long flags; - wd_smp_lock(&flags); - pr_emerg("CPU %d became unstuck TB:%lld\n", cpu, tb); print_irqtrace_events(current); @@ -223,6 +257,7 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb) else dump_stack(); + wd_smp_lock(&flags); cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck); wd_smp_unlock(&flags); } else { @@ -318,13 +353,28 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) tb = get_tb(); if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) { + /* + * Taking wd_smp_lock here means it is a soft-NMI lock, which + * means we can't take any regular or irqsafe spin locks while + * holding this lock. This is why timers can't printk while + * holding the lock. + */ wd_smp_lock(&flags); if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) { wd_smp_unlock(&flags); return 0; } + if (!wd_try_report()) { + wd_smp_unlock(&flags); + /* Couldn't report, try again in 100ms */ + mtspr(SPRN_DEC, 100 * tb_ticks_per_usec * 1000); + return 0; + } + set_cpu_stuck(cpu, tb); + wd_smp_unlock(&flags); + pr_emerg("CPU %d self-detected hard LOCKUP @ %pS\n", cpu, (void *)regs->nip); pr_emerg("CPU %d TB:%lld, last heartbeat TB:%lld (%lldms ago)\n", @@ -334,14 +384,19 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) print_irqtrace_events(current); show_regs(regs); - wd_smp_unlock(&flags); - if (sysctl_hardlockup_all_cpu_backtrace) trigger_allbutself_cpu_backtrace(); if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP"); + + wd_end_reporting(); } + /* + * We are okay to change DEC in soft_nmi_interrupt because the masked + * handler has marked a DEC as pending, so the timer interrupt will be + * replayed as soon as local irqs are enabled again. + */ if (wd_panic_timeout_tb < 0x7fffffff) mtspr(SPRN_DEC, wd_panic_timeout_tb); |